Relaxin as a hormonal aid to evaluate pregnancy and pregnancy loss in bottlenose dolphins (Tursiops truncatus).

This study was conducted to critically evaluate weekly and monthly circulating concentrations of immunoreactive relaxin throughout pregnancies that resulted in live births, stillbirths, and abortions in aquarium-based bottlenose dolphins. A relaxin RIA was used to analyze serum collected during 74 pregnancies involving 41 dolphins and 8 estrous cycles as well as 8 non-pregnant dolphins. Pregnancies resulted in live births (n=60), stillbirths (n=7), or abortions (n=7).

Relaxin and progesterone during pregnancy and the post-partum period in association with live and stillborn calves in bottlenose dolphins (Tursiops truncatus).

The objectives of this study were to validate a relaxin and progesterone RIA for use in bottlenose dolphins, and quantify and characterize both hormones in extracts of placental tissue and serum collected during pregnancy and the post-partum period, and compare the results between dolphins with live and stillborn calves. In Experiment 1, validation of a heterologous relaxin and progesterone RIA involved specific displacement of antibody-bound radiolabeled human relaxin or progesterone in response to increasing volumes of pooled pregnant dolphin serum and amounts of respective hormone standards added to a fixed volume of serum. The displacement curves were considered parallel and additive relative to respective standard curves.

Validation of a homologous canine relaxin radioimmunoassay and application with pregnant and non-pregnant Northern fur seals (Callorhinus ursinus).

The primary objectives of this study were to validate a canine relaxin RIA for use in otariids and phocids and consider practical applications. For 6 captive Northern fur seal females, serum samples were grouped and examined according to pregnancy (n=13), post-partum (n=8) and non-pregnancy (n=6), and, for 2 captive Northern fur seal males, serum samples were grouped and examined together regardless of age (2 mo-15 yrs, n=6). Placental tissue was available for examination from one Northern fur seal, Steller sea lion and harbor seal.

Biological activity of relaxin in porcine milk.

A lactocrine mechanism for delivery of maternally derived relaxin (RLX) into the neonatal circulation as a consequence of nursing has been proposed for the pig. Consistently, immunoreactive porcine RLX was detected in colostrum as well as in the serum of nursing pigs. Concentrations of porcine RLX in milk are highest during early lactation (9-19 ng/mL) and decline to less than 2 ng/mL by postnatal day 14.

Milk-borne relaxin and the lactocrine hypothesis for maternal programming of neonatal tissues.

The fact that all newborn mammals drink milk extends the time frame of maternal influence on development into neonatal life. While the nutritional and immunological benefits of milk are clear, the role of milk as a conduit for bioactive factors with the potential to affect neonatal development is less well defined. Porcine and canine milk contain immunoreactive relaxin (RLX) that is transmitted into the circulation of nursing offspring.

The source and secretion of immunoactive relaxin in rat milk.

The milk of many mammalian species contains hormones and growth factors in addition to nutrients and immunocompetent substances. These factors can be absorbed into the circulation of suckling neonates to exert important effects on metabolism and promote tissue and organ growth. Frequently, there is uncertainty as to whether such substances are gene products of the mammary glands themselves or are produced elsewhere and concentrated from the systemic circulation.

Refinement of a commercial bench-top relaxin assay for pregnancy diagnosis using urine from domestic and nondomestic felids.

Relaxin, a 6-kDa polypeptide hormone, is excreted in the urine during pregnancy in several mammalian species. A recent study showed that detection of urinary relaxin using a bench-top serum assay (Witness relaxin kit, Synbiotics Corp., San Diego, California 92127, USA) can be diagnostic for pregnancy in domestic cats (Felis silvestris catus), but it is unknown whether the bench-top kit is applicable with urine across felid species.

Transmission of relaxin and estrogens to suckling canine pups via milk and possible association with hip joint laxity.

Objective: To determine whether abnormal laxity of hip joints of canine pups with genetic predisposition to hip dysplasia (HD+) is related to ingestion of milk-borne hormones.

Animals: 7 female Labrador Retrievers with HD+ and 8 with low predisposition to hip dysplasia (HD-) and their offspring.

Procedures: Immunoactive relaxin, estrogen, and estrogen precursor concentrations in milk of HD+ lactating bitches and in serum of their pups were compared with those of HD- bitches and pups.

Hormonal changes accompanying cigarette smoke-induced preterm births in a mouse model.

Epidemiologic evidence indicates that maternal smoking increases the risk of preterm birth. While a number of plausible mechanisms for early delivery have been offered, the role of gestational hormones in this smoke-induced outcome is uncertain. Thus, a toxicologic study was performed to examine the effects and underlying hormonal mechanisms of mainstream cigarette smoke (MCS) exposure on gestational duration.

Expression of LGR7 and LGR8 by neonatal porcine uterine tissues and transmission of milk-borne relaxin into the neonatal circulation by suckling.

Estrogen receptor-dependent organizational events between birth [postnatal day (PND) 0] and PND 14 affect development and function of porcine uterine tissues. Observations that uterotrophic effects of relaxin (RLX) in neonatal gilts were inhibited by the antiestrogen ICI 182,780 suggested that a RLX signaling system, capable of cross-talk with the estrogen receptor, evolves during a critical period for uterine programming (PND 0-14). Objectives were to determine 1) effects of age and estrogen exposure from birth on porcine uterine RLX/insulin-like 3 receptor (LGR7/LGR8) expression and 2) whether milk serves as a natural source of RLX in neonatal pigs.

Development, validation, and application of a urinary relaxin radioimmunoassay for the diagnosis and monitoring of pregnancy in felids.

Many nondomestic felids are highly endangered, and captive breeding programs have become essential components of holistic conservation efforts for these species. The ability to diagnose pregnancy early in gestation is fundamental to developing effective breeding programs. The purpose of this study was to develop a radioimmunoassay (RIA) for the detection of urinary relaxin in felids and assess its applicability for early, noninvasive pregnancy diagnosis in domestic cats (Felis silvestris catus) and leopards (Panthera pardus).

The parity-related protection against breast cancer is compromised by cigarette smoke during rat pregnancy: observations on tumorigenesis and immunological defenses of the neonate.

Early pregnancy is a powerful negative risk factor for breast cancer (BCa) in women. Pregnancy also protects rats against induction of BCa by carcinogens such as N-methyl-N-nitrosourea (MNU), making the parous rat a useful model for studying this phenomenon. Smoking during early pregnancy may lead to an increased risk of BCa in later life, possibly attributable to carcinogens in cigarette smoke (CS), or to reversal of the parity-related protection against BCa.

Effects of relaxin in a model of rat adjuvant-induced arthritis.

A reduction in the incidence and severity of rheumatoid arthritis is seen in pregnant women. Relaxin, a hormone of pregnancy, has been implicated in decreased immune responsiveness. Consequently, the effects of relaxin and estradiol valerate, alone or in combination, were assessed in the development of adjuvant-induced arthritis in the rat.

Relaxin concentrations in serum and urine of endangered species: correlations with physiologic events and use as a marker of pregnancy.

Many mammalian species are facing extinction due to problems created by human encroachment, agriculture, pollution, and willful slaughter. Among those at risk are the Asian and African elephant, Sumatran rhinoceros, and giant panda. Conservation groups try to save species in the wild by preserving habitat and limiting animal-human conflicts, often with limited success.

Species and fetal gender effects on the endocrinology of pregnancy in elephants.

Quantitative and temporal progestin profiles vary during gestation in the elephant, sometimes making it difficult to determine if a pregnancy is progressing normally. The aim of the present study was to determine if circulating progestin variability was related to species or fetal gender effects. A similar comparison also was conducted for secretory profiles of prolactin, relaxin, and cortisol.

Immuno-neutralization of circulating relaxin does not alter the breast cancer-protective action of parity in MNU-treated rats.

Early pregnancy and childbirth protects women against future development of breast cancer by an unknown mechanism. Parity likewise reduces mammary cancer incidence in rats exposed to the carcinogen, N-methyl-N-nitrosourea (MNU), providing a model for the human phenomenon. We hypothesized that relaxin, a 6KD luteal mammotropic hormone of pregnancy, might be the anti-cancer pregnancy factor, and that induced relaxin deficiency during rat gestation would restore carcinogen sensitivity.

Serum relaxin concentrations and reproduction in male bonnethead sharks, Sphyrna tiburo.

Relaxin is a 6-kd polypeptide hormone that is responsible for regulating several reproductive processes in female vertebrates, but its role in male reproduction remains unclear. To aid in clarifying this role, the objective of the present study was to investigate changes in endogenous relaxin levels associated with reproductive events in male elasmobranchs, which represent one of only three vertebrate groups known to possess this hormone. Serum relaxin concentrations were measured in 27 immature and 66 mature male bonnethead sharks (Sphyrna tiburo), a species with a well-characterized, seasonal reproductive cycle.

Abnormal relaxin secretion during pregnancy in women with type 1 diabetes.

To test the hypothesis that relaxin may play a role in the fetal abnormalities associated with pregnancy in type 1 diabetic women, we previously compared gestational relaxin concentrations in diabetic and clinically normal women using a porcine relaxin radioimmunoassay (RIA): Serum immunoactive relaxin was significantly (P < 0.001) elevated in the diabetic women. To confirm and extend this work in a larger group of subjects, we have now used an enzyme-linked immunosorbent assay (ELISA) specific for human H2 relaxin (the normal human gene product) to determine immunoactive serum relaxin concentrations in serial samples from 61 Type 1 diabetic and 21 normal pregnant women.